Air-conditioning is normally defined as the control of temperature, humidity, purity, and motion of air in an enclosed space, independent of outside conditions. There exist a variety of apparatus and methods to control the environmental conditions of an enclosed space, stemming from the primitive means of hanging wet grass mats over windows for cooling air by evaporation, to more advanced techniques that employ more sophisticated air-conditioning technology.
For instance, a simple air conditioner, a refrigerant, normally consisting of freon (carbon compounds containing fluorine and chlorine or bromine), in a volatile liquid form, is passed through a set of evaporator coils across which air from inside a room or enclosed space is passed. The refrigerant evaporates and, in the process, absorbs the heat contained in the air. When the cooled air reaches its saturation point, its moisture content condenses on fins placed over the coils. The water runs down the fins and drains. The cooled and dehumidified air is returned into the room by means of a blower. During this process, the vaporized refrigerant passes into a compressor where it is pressurized and forced through condenser coils, which are in contact with the outside air. Under these conditions, the refrigerant condenses back into a liquid form and gives off the heat it absorbed from the air inside the enclosed space. This heated air is expelled to the outside, and the liquid re-circulates to the evaporator coils to continue the cooling process. In some units, the two sets of coils can reverse functions so that in winter, the inside coils condense the refrigerant and heat rather than cool the room or enclosed space. Such a unit is typically referred to as a heat pump, which can selectively cool or heat the enclosed space.
Although air-conditioning units as described above are exemplary, they are expensive to operate as they use a tremendous amount of electrical power, and the refrigerant must be periodically replaced or replenished. Furthermore, the chemicals used in air conditioners contain chlorofluorocarbons, which are proven harmful to humans and the environment. Additionally, air-conditioning units typically re-circulate the air in an enclosed structure, and the re-circulated air eventually becomes stale and impure over time.
Another system of cooling air in an enclosed space is simply by means of passing air through water for cooling the air by means of evaporation. The apparatus used for accomplishing this method of cooling are normally referred to as evaporative coolers. Although evaporative coolers are less expensive to operate than the air conditioners that use refrigerant as discussed above, and they do not re-circulate the air as do the air conditioners, they are not very effective when the 1% coincident wet bulb temperatures are high. Thus, although evaporative coolers are less costly to operate, air-conditioning units are more effective at higher 1% coincident wet bulb temperatures. Furthermore, over time, evaporative coolers tend to use lots of water, and provide a buildup of humidity within the structure which can lead to mildew build-up, and an annoying mildew smell. In order to attain relief, windows in the structure must be opened to release the humid air, or relief vents can be provided for expelling the humid air.
Accordingly, many structures have both an air-conditioning apparatus, and an evaporative cooling apparatus, both of which are used for cooling the internal areas of the structure. However, in order to have both an air-conditioning unit and an evaporative cooler, both must be separately purchased, which is not only very expensive, but also inconvenient and time consuming to install. Additionally, when both an air-conditioning unit and an evaporative cooler unit are installed in combination with a structure, two penetrations into the structure are required which lead into two different sets of duct systems which also must be constructed at considerable cost. A further inconvenience of having both an air-conditioning unit and an evaporative cooler unit is that in order to switch use from one or the other as selectively desired, it must be done manually by either physically adjusting the individual units, or by means of a manual switch located apart from the individual units and normally within the structure.
Some cooling units include both an air-conditioning unit and an evaporative cooler unit that contains a damper and actuator mechanism that moves the damper back and forth from operation of the air-conditioning unit and the evaporative cooler unit, and through the manual operation of a remote control position switch. However, not only is it inconvenient to have to manually operate the remote control position switch, it is not always readily apparent to the user when it is more cost effective and efficient to switch from either the air conditioner unit or the evaporative cooler to the other.
Alternate systems of cooling include the use of chilled water. Water may be cooled by refrigerant at a central location and run through coils at other places. Water may be sprayed over glass fibers and have air blown through it. Dehumidification is achieved in some systems by passing the air through silica gel which absorbs the moisture, and in others, liquid absorbents cause dehydration. Although these systems are exemplary, they use a tremendous amount of water, which can not only be expensive, but not very practical for dryer regions where water is less abundant.
The specific design of air-conditioning systems normally requires the consideration of a variety of variables and circumstances. For instance, some of the self-contained units, described above, serve an enclosed space directly. More complex systems, as in tall or large buildings, use ducts to deliver the cooled air. In the induction system, air is cooled once at a central plant, and then conveyed to individual units, where water is used to adjust the air temperature according to such variables as sunlight exposure and shade. In the dual-duct system, warm air and cool air travel through separate ducts and are mixed to reach a desired temperature. A more simple means of controlling temperature is to regulate the amount of cold air supplied, cutting it off once a desired temperature is reached. Since these types of systems require two distinct sets of ducts, one for carrying cool air and one for carrying warm air, they are normally very expensive to manufacture as a result of the requirement of having two sets of ducts, and very expensive to maintain.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved apparatus for heating and cooling.
Another object of the present invention is to conserve utilities.
Another object of the present invention is to provide an apparatus for heating and cooling that is relatively inexpensive to manufacture.
Still another object of the present invention is to provide an apparatus for heating and cooling having an automatic switching mechanism for selectively and automatically switching operation of the unit between air-conditioning and evaporative cooling when the environmental conditions provide use of one is more efficient and cost effective than the other.
Yet another object of the present invention is to eliminate the need for multiple penetrations through a structure, and the need for multiple duct systems.
Yet still another object of the present invention is to eliminate the need for a user to purchase separate air-conditioning and evaporative cooler units.
And a further object of the invention is to eliminate the need for opening windows for relieving a structure of humid or stale air.
Still a further object of the immediate invention is to provide a heating and cooling unit that uses a common duct system.
Yet a further object of the invention is to reduce energy costs associated with heating and cooling.
And still a further object of the invention is to provide a heating and cooling unit that is easily installed, and easily accessible for servicing and repair.
In addition to the objects mentioned above, the present invention considers heating and cooling systems that use their respective components to additionally provide a ventilating or air circulating system for the structure. Conventional heating, cooling and ventilating systems use the ducting and the blower of the heating and cooling system to provide air circulation for the structure. Typical ventilating systems use the blower to pump air through supply ducting and into the structure, and use return air ducting to receive air from the structure. A conventional ventilating system such as this, provides for circulation or movement of air within the structure.
Conventional ventilating systems circulate air within the structure and require the opening of doors, windows and the like to introduce fresh air into the structure. The opening of doors and/or windows to introduce fresh air is frequently undesirable as it allows outside noise and unfiltered air to enter the structure and provides reduced security for occupants inside the structure. Moreover, when no doors, windows and/or relief vents are open, an undesirable build up of ambient pressure inside the structure can occur. A like ambient pressure build up occurs when conventional evaporative cooling systems are run without opening any doors, windows and/or relief vents. This undesirable build up of ambient pressure can become significant enough to cause discomfort to the occupants inside the structure and may even cause damage to the structure itself.
As previously discussed, evaporative coolers are not very effective when the wet bulb temperature or relative humidity is relatively high. Evaporative coolers are also less effective when the ambient dry bulb temperature is relatively high. An example of this is when the selected or desired temperature inside the structure cannot be satisfied since the evaporative cooling process cannot lower the relatively high temperature of the ambient air to the desired temperature no matter how dry the ambient air is. This can occur even when the relative humidity is low and relative hot dry ambient air is available for evaporative cooling. In this case the evaporative cooler is unable to provide the desired amount of cooling for the structure and air-conditioning is desirable.
Some cooling units that have both an air-conditioning unit and an evaporative cooling unit need to select which unit to operate. One conventional means for selecting between air-conditioning and evaporative cooling uses an internal duct temperature and a predetermined effectiveness of the evaporative cooler to calculate an external ambient temperature and humidity. This calculation can lead to inaccurate results and is not as accurate as taking a direct measurement of the external ambient temperature and humidity. A switching point that is characterized by a predetermined internal duct-ambient temperature and humidity is compared to the calculated (not actual) external ambient conditions and the appropriate cooling device is selected in response to this comparison. For this conventional means, the temperature sensor is located inside ducting that is downstream of the evaporative cooler. This exposes the temperature sensor to relative high velocity air that is substantially unfiltered. Small amounts of dirt and debris can easily damage the temperature sensor and/or cause the temperature sensor to give inaccurate readings. Inaccurate calculation of ambient conditions can result in improper selection of the appropriate cooling device. However, directly measuring external ambient atmospheric conditions is difficult because external effects, such as direct sunlight and exhaust airflow from the unit can easily influence sensor readings
Conventional evaporative cooling systems have a water circulating pump located in a cooling water reservoir that holds an amount of cooling water. The pump moves the cooling water from the reservoir through a cooling water line that is capped at one end. The water line has a quantity of orifices or openings that are located above a cooling pad and upstream of the capped end. The cooling pad is located in a cooling unit inlet airflow path. The cooling pad retains a portion of cooling water that is pumped through and emitted by the water line openings. Unit inlet airflow passing through the cooler pad is evaporatively cooled. Typically, evaporative cooling systems cap off the water cooling line at a location that is downstream of and close to the last opening in the water line. After a time these openings become clogged with mineral deposits from the cooling water. One conventional technique for reducing these mineral deposits bleeds off a portion of cooling water before it reaches the openings This reduces the amount of reservoir cooling water such that an automatic fill valve opens and new water is supplied to the reservoir. This technique tends to reduce mineral build up in the cooling water reservoir but does little to clear openings that become clogged over time.
As discussed earlier, the present invention considers cooling units that have both an air-conditioning unit and an evaporative cooling unit. Such cooling units typically have a damper and actuator mechanism for moving the damper back and forth between operation of the air-conditioning unit and the evaporative cooling unit. One such conventional cooling unit uses pneumatic pressure generated by the blower to actuate the damper. Such units are susceptible to damper movement from wind gusts, resulting in reverse airflow through the damper and loss of cooling flow. When such a unit is operating the air-conditioning unit, the blower operates at low speed and generates low pressures that can provide inadequate damper sealing on windy days. No matter whether the air-conditioning unit or the evaporative cooling unit is operating, positive damper sealing in such units is highly desirable. Hot outside air leaking through the damper seals into the unit or inside cooled air leaking through the damper seals to the outside environment, drastically reduces the cooling efficiency of whichever cooling unit is operating.
In addition, such cooling units typically use a common set of duct work and a common blower for both the air-conditioning unit and the evaporative cooling unit. This creates a problem in that evaporative cooling units operate at a relatively high airflow, desiring relatively large ducts with the blower operating at relatively high speeds, while air-conditioning units operate at relatively low airflow, desiring relatively small ducts with the blower operating at relatively low speeds. Those skilled in the art of designing heating and air-conditioning systems will recognize this to be an airflow mismatch or airflow matching problem. One solution to the problem would be to use small ductwork and a low speed blower for the air-conditioning unit and large duct work and a high speed blower for the evaporative cooling unit. This solution is not only expensive but also negates the reasoning for having a single cooling unit. Conventionally, this problem is solved by using duct work that is sized mid-way between what the air-conditioning unit desires and what the evaporative cooling unit desires along with a selectable dual speed blower having a high speed and a low speed. This typical solution compromises the efficiencies of both the air-conditioning unit and the evaporative cooling unit. Another solution uses duct work sized for the evaporative cooling unit and a dual speed blower with a baffle attached at the blower inlet, to reduce airflow when operating the air-conditioning unit. However, since the baffle is attached to the blower, unless the baffle is removed, the baffle undesirably restricts airflow when the evaporative cooling unit is operating and compromises the efficiency of the evaporative cooling unit.
Accordingly a need exists for a heating, cooling and ventilating system housed in a single enclosure, that combines an air-conditioning or heat pumping apparatus with an evaporative cooling apparatus to provide and maintain a selected comfort level for an enclosed space by controlling that system to select the most effective system cooling apparatus in accordance with the ambient conditions and trends thereof. Moreover, such a heating, cooling and ventilating system would have a means for regulating airflow such that a common blower and a common duct work system could be used by the air-conditioning unit and the evaporative cooling unit without significant reduction in operating efficiency of either unit.